Vasopressin-induced brain edema is mediated by the V1 receptor.

Arginine vasopressin-containing nerve fibers release AVP at extrahypothalamic sites where the hormone appears to regulate brain water. To determine its role in brain edema, we intracerebrally infused AVP, thus bypassing the blood-brain barrier. Thirteen adult cats had 2 mU (5 ng) of AVP infused into the caudate nucleus in 4 microliters CSF: 2 microliters at the start of the experiment and 2 microliters at 2 hr of a 4-hr experiment. Thirteen controls had similar microinfusions into the caudate nucleus of 4 microliters artificial CSF alone. A third group of nine animals had 2 mU AVP infused along with 50 ng of the V1 receptor antagonist (Manning compound). A fourth group of 10 animals had AVP infused along with 50 ng of a V1/V2 receptor antagonist (SK&F 101926). After 4 hr the brains were removed, and water content was measured in anterior, middle, and posterior areas in gray and white matter. We found that animals given AVP had a statistically significant increase in water content in both the gray (F = 7.1, p = 0.0002) and white matter (F = 9.4, p = 0.0001) compared with controls. Both the V1 and the V1/V2 antagonists blocked the increase in water content. We conclude that the V1 AVP receptor is important in water regulation.